early 60s Zenith, turns on, poor picture

[jsowers]

Have you tried changing the channel on the RF modulator to 4 (and the TV channel to 4)? Also the fine tuning ring on the TV around the channel selector could be all you need to tweak. You didn't mention that, so I thought I would, just in case.

Can you find a VCR and a tape to use instead of a Blu-Ray? Also make sure the balun (that twin-lead to screw-on F connector adapter for cable) is working and connected to the screw terminals on the back.